1. Field of the Invention
The present invention relates to a method of transferring semiconductor processing-target members (hereinafter, referred to as “wafers”) among process chambers of a semiconductor processing apparatus.
2. Description of the Related Arts
In a semiconductor processing apparatus, especially, an apparatus in which a processing target is processed in a pressure-reduced state, it has been demanded to improve the efficiency of a process of a wafer that is a processing target as well as finely-tuned and accurate processes. Therefore, there has been recently developed a multi-chamber apparatus in which plural process chambers are provided while being connected in order to enhance the efficiency of productivity per installation area for a clean room. In such an apparatus in which the plural process chambers are provided for processing, the pressure of a gas in each process chamber can be reduced, and the process chambers are connected to transport chambers in which robots for transferring wafers are provided.
Among the multi-chamber apparatuses, an apparatus having a structure called as a cluster tool in which process chambers are radially connected around transport chambers has been widely spread. However, the apparatus of the cluster tool requires a large installation area. Especially, the apparatus involves a problem that the installation area becomes much larger along with a large diameter of a wafer in recent years. In order to solve the problem, an apparatus having a structure called as a linear tool has appeared (for example, refer to Japanese Patent Application Laid-Open No. 2007-511104).
The structure of the linear tool is characterized in that plural transport chambers are provided, process chambers are connected to the respective transport chambers, and the transport chambers are directly connected to each other or connected to each other while interposing spaces (hereinafter, referred to as “buffer rooms”) therebetween to pass and receive wafers.
The structure of the linear tool has been proposed to reduce the installation area as described above. On the other hand, some proposals in terms of improvement of productivity have been made. In order to improve productivity, it is important to reduce the processing time and to efficiently carry wafers. Especially, some proposals have been made in terms of efficient transferring methods. As a representative method, there has been known a scheduling method. In the scheduling method, transferring operations are determined in advance, and wafers are transferred on the basis of the transferring operations. As an example of determining the transferring operations, there has been proposed a method in which wafers are allocated to the process chambers as destinations in the order of process completion time from the fastest process chamber, and the transferring operations are determined (refer to Japanese Patent Application Laid-Open Publication No. 10-189687).